Add a configuration option Module.SDL_numSimultaneouslyQueuedBuffers to allow user code to configure how many SDL audio buffers to keep simultaneously queued up for the audio backend. More buffers means less change of starving (and cracking audio), but increases latency. Fewer buffers lower the latency at the risk of playback glitches. Make minimum audio buffer size 128, which should be way below anything reasonable already. Clean up commented out code.